Functional fluid compositions



United States Patent 3,244,627 FUNCTIONAL FLUID COMPOSITIONS John O.Smith, Swampseott, Mass, and Kenneth L.

McHugh, Kirkwood, Mo., assignors to Monsanto Research Corporation, St.Louis, Mo., a corporation of Delaware No Drawing. Filed Jan. 23, 1962,Ser. No. 168,244 Claims. (Cl. 25233.6)

This invention relates to liquid fluids of high thermal stability andmore particularly provides functional fluids comprising polyphenylethers and certain organometallic compounds as adjuvants therefor.

The polyphenyl ethers are known compounds which have found wideapplication as functional fluids owing to their very good thermalstability, lubricity, and resistance to foam. For example, they havebeen found to be valuable as hydraulic fluids, as heat-exchange media,as atomic reactor coolants, as diffusion pump fluids, as lubricants inmotor operation generally, and particularly as jet engine lubricants.

With recent changes in the design of aircraft engines, there is a demandfor lubricants which will perform satisfactorily under conditions farmore rigorous than ever contemplated in the past. A particularlyimportant requirement for lubricants intended for use in the newlydesigned engines is that their viscosity and lubricity be unaffected bythe high temperatures to which they are necessarily subjected.

As is known in the art, petroleum lubricants generally comprise, inaddition to the petroleum base stock, addi- I tives or adjuvants whichimpart specifically desired properties to the base stock, e.g.,rust-inhibitors, antioxidants, extreme pressure-resisting agents,lubricity improver's, detersives, etc. The additives proposed heretoforehave been designed to accommodate the requirements of petroleum basestocks for lubrication in conventional equipment such as internalcombustion engines of the automotive type, diesel engines and the like.One feature in common with respect to these various applications wasthat the temperature of use was not excessive, i.e., it may vary fromabout 40 F. to 400 F. With the advent of extremely high speed aircraftof the jet type, it was found that neither the petroleum base stock northe conventional additives used therewith were practical, because thelubricant and the additives had to be eifective at temperatures whichwere above the decomposition points of the known compositions, e.g., attemperatures which were generally within the range of 500 F. to 700 F.It was also found that when conventional additives were employed withfunctional fluids having higher thermal stability than that possessed bypetroleum base stocks, the additives did not perform in a predictablemanner, i.e., a material possessing antioxidant effect or an extremepressure resisting eflect with the petroleum hydrocarbon lubricantsgenerally did not 'possess such effects when used with the polyphenylether fluids.

Although the polyphenyl ethers possess extremely good thermal stabilityat temperatures of, say, over 550 F., they tend to deteriorate, notbecause of a decomposition reaction, but because at the highertemperatures they become quite readily oxidizable. The lubricity of thepolyphenyl ethers is thereby impaired, since the oxidation products donot possess lubricating properties; moreover, the chainge in viscositywhich is a consequence of the oxidation not only makes for inefliciency,but also may clog up the moving parts of the mechanism which thelubricant was originally intended to protect. Hence,

when the polyphenyl ethers are to be used at the higher temperaturesunder conditions requiring exposure to air, it is necessary to inhibitoxidation phenomena which the higher temperatures favor.

The polyphenyl ethers, like conventional petroleum lubricants, are alsosomewhat deficient with respect to lubricity, anti-wear and extremepressure-resisting properties, e.g., breakdown of lubricant film occursunder some conditions of use, particularly at the extreme pressuresencountered in gear lubrication. Here again, conventional lubricity,anti-wear and extreme pressure-resisting (E.P.) additives are generallyineifective with the polyphenyl ethers and do not withstand the veryhigh temperatures at which the high thermal stability of the etherscould make them of most use.

Accordingly, an object of the present invention is the provision ofimproved polyphenyl ether fluid compositions. Another object of theinvention is the provision of polyphenyl ether compositions havingimproved antioxidant properties. Still another object of the inventionis the provision of polyphenyl ether compositions having improvedlubricity. A further object is the provision of polyphenyl ethercompositions having improved anti-wear properties. Still a furtherobject is the provision of polyphenyl ether compositions having improvedextreme pressure-resisting properties. A most important object of theinvention is the provision of polyphenyl ether compositions whichpossess an improved resistance to oxidation at temperatures of over 550F.

These and other objects hereinafter disclosed are provided by theinvention wherein there is employed as additive for the polyphenyl etherliquid fluids a heavy metal bis(N,N-diorganodithiocarbamate) of theformula R s s R R 1'r- 'l-S M S- i R in which R and R individually arehydrocarbon radicals which are free of olefinic and acetylenicunsaturation and contain from 1 to 12 carbon atoms and together completewith the nitrogen to which they are attached, a saturated heterocyclicring of from 5 to 6 members and from 4 to 10 carbon atoms, and M is abivalent heavy metal ion.

Compounds of the above formula in which R and R are hydrocarbon aremetal bis(N,N-dialkyldithiocarbamates), orbis(N,N-diaryldithiocarbamates), or his- [N,N-bis( aralkyl)dithiocarbamates] or bis [N,N-'bis (alkaryl)dithiocarbamates], orbis(N,Ndicycloalkyldithiocarbamates), orbis(N-alkyl-N-aryldithiocarbamates), orbis(N-alkyl-N-aralkyldithiocarbamates), or bis(N-aryl-N-aralkyldithiocarbamates), orbis(N-alkaryl-N-cycloalkyldithithiocarbamates), etc.; i.e., the R and Rof the above formula may be alkyl, -aryl, aralkyl, alkaryl orcycloalkyl, and they may be the same or different. When taken togetherwiththe nitrogen atom to which they are attached, R and R complete asaturated heterocyclic nitrogen ring of from 5 to 6 members, e.g., thepyrrolidine, piperidine, morpholine, pyrazolidinedione, orthiomorpholine ring, etc.

The heavy metal ion may be, e.g., bivalent zinc, cadmium, mercury,indium, gallium, germanium, tin, lead, vanadium, chromium, molbydenum,tungsten, platinum, manganese, iron, cobalt, silver, nickel, etc. Thebivalent heavy metal ions of Groups I-IV and VIIVIII are preferred.

The polyphenyl ethers to which this invention pertains can berepresented by the structure where n is a Whole number from 2 to 5. Thepreferred polyphenyl ethers are those having all their ether linkages inthe meta position since the all-meta linked ethers are the best suitedfor many applications because of their wide liquid range and high degreeof thermal stability. However, mixtures of the polyphenyl ethers, i.e.,either isomeric mixtures or mixtures of homologous ethers, can also beused to obtain certain properties, e.g., lower solidification points.Examples of the polyphenyl ethers contemplated are thebis(phenoxyphenyl)ethers, e.g., bis(m-phenoxyphenyl)ether, thebis(phenoxyphenoxy)benzenes, e.g., m-bis(m-phenoxyphenoxy)benzene,m-bis(p-phenoxyphenoxy)benzene, o-bis(o-phenoxyphenoxy)benzene, thebis(phenoxyphenoxyphenyl)ethers, e.g.,bis[m-(m-phenoxyphenoxy)phenyl]ether,bis[p-(pphenoxyphenoxy)phenyl]ether, m [(mphenoxyphenoxy)(o-phenoxyphenyl)]ether and thebis(phenoxyphenoxyphenoxy)benzenes, e.g.,m-bis[m-(m-phenoxyphenoxy)phenoxy]benzene, p-bis[p (m phenoxyphenoxyphenoxy] benzene or m-bis [m- (p-phenoxyphenoxy) phenoxyJbenzene. It isalso contemplated that mixtures of the polyphenyl ethers can be used.For example, mixtures of polyphenyl ethers in which the non-terminalphenylene rings (i.e., those rings enclosed in the brackets in the abovestructural representation of the polyphenyl ethers contemplated) arelinked through oxygen atoms in the meta and para positions, have beenfound to be particularly suitable as lubricants because such mixturesposses low solidification points and thus provide compositions havingWider liquid ranges. Of the mixtures having only meta and para linkages,a preferred polyphenyl ether mixture of this invention is the mixture ofS-ring polyphenyl ethers where the non-terminal phenylene rings arelinked through oxygen atoms in the meta and para position and composed,by weight, of about 65% m-bis(m-phenoxyphenoxy)benzene, 30% m [(mphenoxyphenoxy) (p-phenoxyphenoxy)]benzene and 5%mbis(p-phenoxyphenoxy)benzene. Such a mixture solidifies at about l0 F.,whereas the three components solidify individually at temperatures abovenormal room temperatures.

The aforesaid polyphenyl ethers can be obtained by the Ullmann ethersynthesis which broadly relates to ether forming reactions, e.g., alkalimetal phenoxides such as sodium and potassium phenoxides are reactedwith aromatic halides such as bromobenzene in the presence of a coppercatalyst such as metallic copper, copper hydroxides, or copper salts.

The presently useful metal diorganodithiocarbamates may be readilyprepared, e.g., by reaction of a secondary amine with carbon disulfideand ammonium hydroxide or alkali metal hydroxide to obtain the ammoniumor alkali metal salt and then reacting two moles of said salt with onemole of a metal salt, e.g., the acetate, thus:

Copper bis(N,N-dibutyldithiocarbamate),

needles, M.P. 677l C.

Cobalt bis N,N-dibutyldithio carbamate plates, M.P. 127-131 C.

Nickel bis (N,N dibutyldithiocarbamate),

plates, M.P. 82-84" C.

Copper bis(N,N-diphenyldithiocarbamate), brown powder, M.P. 300-304" C.

Cobalt bis(N,N-diphenyldithiocarbamate), green powder,

M.P. over 340 C.

green black deep green olive drab Nickel bis(N,Ndiphenyldithiocarbamate), pea-green powder, M.P. 290-3l5 C.

Copper bis(morpholinodithiocarbamate), dark brown powder, M.P. 310 C.

Cobalt bis(morpholinodithiocarbamate), green powder,

M.P. 290 C.

Nickel bis(morpholinodithiocarbamate), pea-green powder, M.P. 345 C.

Copper bis (piperidinodithiocarbamate), dark brown powder, M.P. 210 C.

Cobalt bis(piperidinodithiocarbamate), green powder,

M.P. 250-252 C.

Nickel bis(piperidinodi'thiocarbamate), pea-green powder, M.P. 289-295"C.

Manganous bis(piperidinodithiocarbamate), M.P. 162- Other presentlyuseful diorganodithiocarbamates are,

Zinc bis N,N-dioctyldithiocarbamate Tin bis (N,N-dibenzyldithiocarbamateNickel bis N,N-didodecyldithiocarb amate Iron bisN,N-di-4-tolyldithiocarbam ate) Cobalt bisN,N-dicyclopentyldithiocarbamate) Copper bis N,N-bis Z-phenylethyldithiocarbamate] Cadmium bis(N-ethyl-N-phenyldithiocarbamate) Silver bis(N-cyclohexyl-N-phenyldithiocarbamate Nickel bisN,N-di-u-naphthyldithiocarbamate) Tungsten bis(N,N-dimethyldithiocarbamate Indium bis N,N-dixylyldithiocarbamate)Mercury bis [N,N-bis (4-isopropylphenyl dithiocarbamate] Gallium bis[N-hexy-N- (Z-methylcyclopentyl) dithiocarbamate] Molybdenum bis(N-benzyl-N-phenyldithiocarbamate) Manganese bisN,N-dipentyldithiocarbamate) Germanium bisN,N-difiuorenyldithiocarbamate) Chromium bis(N,N-dihexyldithiocarbamate) Platinum bis N,N-diisopropyldithiocarbamateNickel bis N,N-diacenaphthenyldithiocarbamate Copper bis [N,N-bis(tetrahydronaphthyldithiocarb amate) Cobalt bisN,N-dipyrrolidinodithiocarbamate) Indium bisN,N-dithiomorpholinodithiocarbamate Nickel bis N,N-bis 3,5 -dioxopyrazolidino dithocarbamate] Cadmium bis(N,N-dimorpholinodithiocarbamate,

Copper bis (N-phenyl-N-piperidinodithiocarbamate).

The metal diorganodithiocarbamates are combined with the fiuidpolyphenyl ethers to the extent of 0.5% to 5.0% by weight, dependingupon the nature of the dithiocarbamate and of the ether fluid and uponthe adjuvant effect desired. The heavy metal diorganodithiocarbamatesgenerally have a beneficial effect on the polyphenyl ether in that thereis obtained improvement in stability to oxidation and/or increasedlubricity and/or increased resistance to wear and extreme pressure. Allof these benefits do not necessarily result from the use of oneadditive, although a number of these compounds do confer a plurality ofsuch effects when employed with the ethers within the above-stated rangeof concentration. Whether or not a desired adjuvant effect is obtainedis readily determined by use of conventional testing procedures known tothose skilled in the art. The effectiveness of the present additives isalso not the same over the entire range of concentration; for example,while it has been noted that in most cases the ability of the agent withrespect to anti-wear and extreme pressure lubrication improves markedlyas the concentration is increased, the reverse may be true insofar asantioxidant effect is concerned, lower amounts of the additive oftenresulting in a greater degree of stability to oxidation at the hightemperatures than are attained by use of the greater amounts of the sameadditive.

The invention is further illustrated by, but not limited to, thefollowing examples:

Example 1 The antioxidant effect of some metalbis(N,N-diphenyldithiocarbamates) on a polyphenyl ether fluid wasdetermined by bubbling air through a 20 milliliter sample 'at 600 F. for48 hours and then determining the viscosity (at 100 F) and percent lossin weight of the treated sample. The percent change in viscosity (beforeand after oxidation) was taken as an index of antioxidant activity.Since the presence of metals also has been found to have an effect onthe oxidation of polyphenyl ether fluids at high temperatures, thetesting was also conducted in the presence of metals. In order to de-'termine metal eifect, one set of duplicate samples of ether fluid plusadditive contained copper, steel, aluminum and silver wires, whereasanother duplicate set contained only the ether fluid and additive.Duplicate sets of no-additive controls Were also employed, .one set ofonly the ether fluid and another set in which the metal wires wereimmersed in the ether fluids. Using Weighed pieces of metal, theanti-corrosive effect of the additive could also be obtained.

' Each of the dithiocarbamates shown below was tested :for use asantioxidant at the indicated concentration, for

a mixture of polyphenyl ethers consisting by weight of 65% of m-bis(m-phenoxyphenoxy)benzene, 30% of m-[(m-phenoxyphenoxy)(p-phenoxyphenoxy)]- benzene,

5% of m-bis(p-phenoxyphenoxy)benzene.

' The following results were obtained:

Viscosity Increase, Metal bis(N,N-d1phenyld1tlno- Conen, wt. Percentearbamate) Percent N0 Wires With Wires Example 2 Employing the testingprocedure of Example 1, except that air-flow was conducted for only 24hours, antioxidant activity was determined for the dithiocarbamates'shownbelow. The percent increases in viscosity in the absence orpresence of the copper, aluminum, and steel Wires, using the mixture ofpolyphenyl ethers described -in Example 1 at the indicated concentrationof the dithiocarbamate were found to be as follows:

In this example, nickel bis(N,N-di-n-butyldithiocarbamate) was tested ata 1.0 percent by weight concentration as an intioxidant for a mixture ofpolyphenyl ethers consisting about 90 percent by weight of etherscontaining 5 benzene rings and 4 oxygen atoms, with the balance beingethers containing 4 benzene rings and 3 oxygen atoms. Testing wasconducted at 600 F., as in Example 1, except that there were used onlycopper, aluminum and iron wires. There was thus obtained a viscosityincrease of only 0.16% for the test specimen containing thedithiocarbamate as compared to 26.9%, the viscosity increase of thepolyphenyl ether mixture, alone.

Example 4 The anti-wear and extreme pressure lubrication characteristicsof copper bis(N,N-dibutyldithiocarbamate) in polyphenyl ether fluidswere evaluated by means of the Shell 4-Ball Extreme Pressure Tester andthe Shell 4- Ball Wear Machine measuring the scar diameter at 40 kg. inmillimeters.

The l-Ball Tester consists of four balls of stainless steel arranged inthe form of an equilateral tetrahedron. The basic elements are threelower balls held immovably in a clamp to form a cradle in which a fourthor upper ball is caused to rotate about a vertical axis under prescribedconditions of load and speed. The contacting surfaces on the 4-ball typeapparatus are geometrically well-defined, thus providing obviousadvantages in the study of wear and friction phenomena.

The points of contact are lubricated by immersion in the fluid undertest, which is held in a cup surrounding the 4-ball assembly. Thecircular scars worn in the surface of the three stationary balls weremeasured by means of a low power microscope. Using a 1.0 Weight percentconcentration of the copper bis(N,N-dibutyldithiocarbamate) with thepolyphenyl ether mixture of Example 2, there was obtained a scardiameter of 0.99 mm. at 167 F. and 40 kg, as compared to 1.82 mm., thesimilarly obtained value for the mixture of ethers in the absence of anadditive.

The weld point of the balls was determined by having them immersed inthe test lubricant [the polyphenyl ether of Example 1 containing 1.0weight percent of copper bis(N,N-dibutyldithiocarbamate)] and graduallyincreasing the load on the balls by increments of 10 kg. until the ballswere welded together in a one minute test period. A value of 310 kg. wasobtained as against kg. for the mixture of ethers, alone.

The polyphenyl ether fluid containing copper N,N-dibutyldithiocarbamateas additive was also submitted to the Falex antiweld test [see, e.g.,the articles by V. A. Ryan in Lubrication Engineering, September 1946,and by S. Kyropoulos in Refiner Natural Gasoline Mfit, 18, 3224 (1939)].In this procedure, there was employed a Faville-Le Vally Falex lubricanttesting machine with heating element, 4,500 lb. pressure gage indicatinghearing loads, calibrated, circular, toother loader capable of providingwear estimates, and torque indicating gage. The machine is essentially adevice in which a pin is rotated between two V-shaped bearing blockswhich are immersed in an oil cup containing 55 ml. of the lubricantwhich is to be tested. The bearing blocks are inserted in self-aligningrecesses in the short lever arms, or jaws, of the loading-applyingmechanism. Pressure is applied through the loading mechanism which fitsloosely over the bifurcated ends of the long lever arms. The ratchetwheel is turned up by hand until the loading mechanism takes hold, whichis indicated by registration of applied load on its attached gage.Additional load is applied by engaging the load applying arm with theratchet Wheel. The eccentric motion of the load applying arm increasesthe application of load, one tooth at a time. The entire mechanism isfree to swing about its axis, this tendency to turn being resisted bythe syphon operated gage which registers torque in pound-inches. In thepresent test, the machine was operated at 290 rpm.

The Falex test value for the mixture of polyphenyl ethers of Example 1containing 1.0 percent by weight of copper bis(N,Ndibutyldithioearbamate) was 2250, whereas that for said ether mixturealone was 500.

The metal bis(diorganodithiocarbamates) possess adjuvant effect for thepolyphenyl ether functional fluids, generally. Thus, instead of themixture of 65% by weight of m-bis(m-phenoxyphenoxy)benzene, 30% byweight of m-[ (m-phenoxyphenoxy) (p-phenoxyphenoxy)] benzene and byweight of m-bis(p-phenoxyphenoxy) benzene which is used in Examples 1, 2and 4, the polyphenyl ether component may be any one polyphenyl etherhaving from 4 to 7 benzene rings. For example, the copperbis(N,N-diphenyldithiosarbamate) of Example 1 or the cobaltbis(N,N-dimorpholinodithiocarbamate) of Example 2 is a very goodantioxidant for any one of the three ethers of the polyphenyl ethermixture of Example 1, as well as for such other polyphenyl ethers asp-bis[p-(m-phenoxyphenoxy)phenoxy]benzene, or m- [(m-phenoxyphenoxy) (ophenoxyphenoxy) ]benzene, or m-bis[m- (p-phenoxyphenoxy)phenoxy]benzene,or mixtures thereof in any proportion. Lubricant mixtures of ethers aregenerally so constituted as to give simultaneously an optimum of thermalstability and lubricity at the temperatures to which they will beexposed in operation; but since the polyphenyl ethers, generally, arebenefited by the present metal bis(N,N-diorganodithiocarbamates) withrespect to increasing stability to oxygen and/ or film strength underconditions of high pressure at high temperatures, mixtures havingvarying proportions of the ethers are advantageously modified.

It is evident from the data presented above that addition of the presentdithiocarbamates to the polyphenyl ethers results in one or morebeneficial effects, i.e., there is brought about increased resistance tooxygen and/ or improvement in stability at operating conditionsinvolving high pressure and temperature. At the same time, there may begenerally decreased attack to metal so that anticorrosive etfect isoften demonstrated.

Since the quantity of the metal bis(N,N-diorganodithiocarbamate) whichis employed with the polyphenyl ether fluid will vary with adjuvanteffect sought, with the nature of the polyphenyl ether and the nature ofthe individual adjuvant, it is evident that no rigid limits of adjuvantcontent can be set forth. For many purposes, particularly forantioxidant and anti-corrosive effects, very low quantities, say,quantities of as low as 0.01% by weight based on the weight of thepolyphenyl ether fluid, are satisfactory. For other purposes, e.g.,extreme pressure-resisting effect, higher concentrations will be moreadvantageous. Generally, polyphenyl ether compositions comprising from0.01% to 10% by weight of the present additive demonstrate adjuvanteffect. At concentrations of up to 10%, optimum improvement of thepolyphenyl ethers is obtained with respect to antioxidant and lubricityand solubility of the additive in the polyphenyl ethers is generallyrealized. Determination of the optimum quantities is readily conductedby routine procedures, as Will be apparent to those skilled in the art.Hence, the amount of the dithiocarbamate to be used can best beexpressed simply as an adjuvant amount. Variations or modifications ofthe compounds and quantities employed in the examples can be made toaccommodate diiferent requirements, so long as the additive belongs tothe general class of organometallic compounds hereinbefore defined andthe polyphenyl ether fluid consists of polyphenyl ethers having from 4to 7 benzene rings.

Although the metal bis(N,N diorganodithiocarbamates) confer a variety ofbeneficial properties to the polyphenyl ether fluids, they may be usedwith other additives, e.g., pour point depressants, viscosity indeximprovers, crystallization suppressants, dyes, etc.

Other modes of applying the'princi-ples of this invention may beemployed instead of those specifically set forth above, changes beingmade as regards the details herein disclosed, provided the elements setforth in any of the following claims, or equivalents thereof may beemployed.

What We claim is:

1. A functional fiuid composition consisting essentially of a polyphenylether of the formula i 1 L J.

wherein n is a whole number of from 2 to 5 and from 0.01% to 10%, byweight of the ether, of a dithiocarbamate of the formula 3 s R I H HRNG-S-M-SCNR in which R and R individually are hydrocarbon radicalswhich are free of olefinic and acetylenic unsaturation and contain from1 to 12 carbon atoms and together complete, with the nitrogen to whichthey are attached, a saturated heterocyclic ring of from 5 to 6 membersin the ring and a total of from 4 to 10 carbon atoms, and M is abivalent heavy metal ion.

2. The composition defined in claim 1, further limited in that thedithiocarbamate is cobalt bis(N,N-diphenyldithiocarbamate).

3. The composition defined in claim 1, further limited in that thedithiocarbamate is copper bis(N,N-diphenyldithiocarbamate).

4. The composition defined in claim 1, further limited in that thedithiocarbamate is nickel bis(N,N-diphenyldithiocarbamate 5. Thecomposition defined in claim 1, further limited in that thedithiocarbamate is copper bis(N,N-dibutyldithiocarbamate).

6. The composition defined in claim 1, further limited in that thedithiocarbamate is cobalt bis(N,N-dibutyldithiocarbamate 7. Thecomposition defined in claim 1, further limited in that thedithiocarbamate is cobalt bis(piperidinodithiocarbamate 8. Thecomposition defined in claim 1, further limited in that thedithiocarbamate is cobalt bis(morpholinodithiocarbamate) 9. Thecomposition defined in claim 1, further limited in that thedithiocarbamate is copper bis(piperidinodithiocarbamate).

10. The composition defined in claim 1, further limited in that thedithiocarbamate is nickel bis(N,N-dibutyldithiocarbamate).

References Cited by the Examiner UNITED STATES PATENTS 2,629,694 2/1953Woods et al. 252400 XR 2,681,891 6/1954 Bos et al 252--- 2,813,07611/1957 Edelman et al. 252-75 XR FOREIGN PATENTS 851,651 10/1960 GreatBritain.

JULIUS GREENWALD, Primary Examiner.

R. D. LOVERING, Assistant Examiner,

1. A FUNCTIONAL FLUID COMPOSITION CONSISTING ESSENTIALLY OF A POLYPHENYLETHER OF THE FORMULA